diff options
author | Greg Thelen <gthelen@google.com> | 2013-04-30 22:26:48 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-05-01 00:04:00 (GMT) |
commit | 421348f1ca0bf17769dee0aed4d991845ae0536d (patch) | |
tree | b4bc4ba3b50909de4885370d1a0656ca916e82db /fs/dcache.c | |
parent | b4ea2eaa11fa2588c241a80d6d1e59f0f68f7b29 (diff) | |
download | linux-421348f1ca0bf17769dee0aed4d991845ae0536d.tar.xz |
fs/dcache.c: add cond_resched() to shrink_dcache_parent()
Call cond_resched() in shrink_dcache_parent() to maintain interactivity.
Before this patch:
void shrink_dcache_parent(struct dentry * parent)
{
while ((found = select_parent(parent, &dispose)) != 0)
shrink_dentry_list(&dispose);
}
select_parent() populates the dispose list with dentries which
shrink_dentry_list() then deletes. select_parent() carefully uses
need_resched() to avoid doing too much work at once. But neither
shrink_dcache_parent() nor its called functions call cond_resched(). So
once need_resched() is set select_parent() will return single dentry
dispose list which is then deleted by shrink_dentry_list(). This is
inefficient when there are a lot of dentry to process. This can cause
softlockup and hurts interactivity on non preemptable kernels.
This change adds cond_resched() in shrink_dcache_parent(). The benefit
of this is that need_resched() is quickly cleared so that future calls
to select_parent() are able to efficiently return a big batch of dentry.
These additional cond_resched() do not seem to impact performance, at
least for the workload below.
Here is a program which can cause soft lockup if other system activity
sets need_resched().
int main()
{
struct rlimit rlim;
int i;
int f[100000];
char buf[20];
struct timeval t1, t2;
double diff;
/* cleanup past run */
system("rm -rf x");
/* boost nfile rlimit */
rlim.rlim_cur = 200000;
rlim.rlim_max = 200000;
if (setrlimit(RLIMIT_NOFILE, &rlim))
err(1, "setrlimit");
/* make directory for files */
if (mkdir("x", 0700))
err(1, "mkdir");
if (gettimeofday(&t1, NULL))
err(1, "gettimeofday");
/* populate directory with open files */
for (i = 0; i < 100000; i++) {
snprintf(buf, sizeof(buf), "x/%d", i);
f[i] = open(buf, O_CREAT);
if (f[i] == -1)
err(1, "open");
}
/* close some of the files */
for (i = 0; i < 85000; i++)
close(f[i]);
/* unlink all files, even open ones */
system("rm -rf x");
if (gettimeofday(&t2, NULL))
err(1, "gettimeofday");
diff = (((double)t2.tv_sec * 1000000 + t2.tv_usec) -
((double)t1.tv_sec * 1000000 + t1.tv_usec));
printf("done: %g elapsed\n", diff/1e6);
return 0;
}
Signed-off-by: Greg Thelen <gthelen@google.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r-- | fs/dcache.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index e8bc342..e689268 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1230,8 +1230,10 @@ void shrink_dcache_parent(struct dentry * parent) LIST_HEAD(dispose); int found; - while ((found = select_parent(parent, &dispose)) != 0) + while ((found = select_parent(parent, &dispose)) != 0) { shrink_dentry_list(&dispose); + cond_resched(); + } } EXPORT_SYMBOL(shrink_dcache_parent); |